# -- coding: utf-8 --
# sum = 1 
# for num in range (1,101):
	# sum = num * sum
# print num
# print sum


# b = 2
# sum = 0.0
# for a in range (1,100):
	# sum = 1.0 /( a * b ) + sum
	# a += 1
	# b += 1 

# print sum

print 'we can caculate 1/a*b '
print 'please input a'
a = input()
print 'please input b'
b = input()
dev = b - a 
print'pleas input An'
an = input()
sum = 0

for i in range(a,an + 1 ):
	sum += 1.0/(i*b)
	i = i + dev 
	b = b + dev 
	
print i 
print  sum
